<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Document</title>
  <style>
    .box {
      width: 500px;
      height: 500px;
      background-color: #ccc;
      color: #fff;
      text-align: center;
      font-size: 100px;
    }
  </style>
</head>

<body>
  <div class="box"></div>
  <script>
     const box = document.querySelector('.box')
    let i = 0
    function res() {
      box.innerHTML = ++i
    }
    box.addEventListener('mousemove', throttle(res, 1000))
    function throttle(fn, time) {
      let start = 0
      function fun() {
        let now = +new Date()
        if (now - start >= time) {
          fn()
          start = now
          console.log(start);
        }
      }
      return fun
    }
    console.log(throttle(res, 1000));

  </script>
</body>

</html>